Combination mill and process of efficient operation thereof



P. c. VAN ZANDT. Y COMBINATION MILL AND PROCESS 0F EFFICIEN'T OPERATION THEREOF.

' APPLICATION FILED O CT- Z, 19H5. 1,361,205. Patented Dec. "7, 1920.

5MB. 5 l

River Forest, Chicago, in the county of other physical characteristics.

UNITED STATES PATENT O EFICE.

PAUL c. vAN zAND'r, OE CHICAGO, ILLINOIS, AssIGNOR To ALLIs-CHALMERS MANU.

FAOTURING COMPANY, OF MILWAUKEE, WISCONSIN, A CORPORATION OF DELA- WARE.

COMBINATION MIL-L AND PROCESS-OE EFEICIEN'I OPERATION THEREOF.

Specification of Letters Patent.

1,361,205. Patented Dec. 7, 1920.

Ap'plication inea october 2, 191e. 4serial Nc. 123,783.

To all whom may concern. there are grinding bodies of certain physical Be it known that I, PAUL C. VAN ZANDT, characteristics and in the other chamber of a citizen Y'of the United States, 'reslding at. which there are grinding Cook and State 'oef' Illinois, have invented aV Prior practice has established-the lawithat certain new and useful Improvement in the most efficient point to which to charge Combination Mills and Processes of Eflia/horizontal rotarycomminuting mill with bodies having cient' Operation Thereof, of which the folgrinding bodies, is'at or near the centerline lowing is a specification. of the mill, and that specifically heavy A This invention relates to mills for combodies are more effective in comminuting minuting "cement-making materials, lcoal, due to their greater weight per unit volume.4 rock, ore and the like, more especially com- It may here be mentioned that if a mill is bination mills, and to the-process of eflicient lcharged to the centerline withgrinding operation of such combination mills. bodies alone, the combined charge of the The Object of the invention is to provide material and grinding bodies will 'not exa combinationmill and a process of efficient tend an appreciable amount above the cenoperation thereof, producingrw` a maximum terline, as most of the material lodges in the rate of 'comminutingoof the materials 'to a' lvoids between the grinding bodies. It has predetermined degree of ineness with a also been .established that when so loaded a minimum .expenditure of energy per )unit mill will operate with maximum capacity; weight or bulk of .finished product. The it will also require maximum total power to process is eected'by apportioning the work rotate the mill; but in spiteof the fact that done in the chambers of the combination the power isa maximum, the efiiciency is mill. Such apportionment may be accomalso a maximum, that is, plished by a relative variation of the volu pended per unit of material ground is a metric capacity of the several. chambers of minimum. When the mill is loaded anv apthe combination mill injany manner, as, for preciableamount either above or below the instance, by varying either the lengthor the centerline, the capacity, power and. efliciency diameter or both, of` one or more of the materially decrease, the total power dechambers. The invention further contemcreasing less rapidly .than the total capacity.

plates the provision-of other detailsof' com- It has been customary invt'heconstruction bination mill constructionwhereby the cost of cpmbination comminuting mills of the duced to a minimum.

In grinding withv tumbling comminnting A bodies it is oundl that the eficiency inof such diameters and lengths,'and arbicreases, up toa point where the mass is '.at such a point, as to produce the predetermany times greater than that of a particle vmined size of each grinding chamber. After Yof installation and of maintenance are reprior art, to arbitrarily predetermine Vthe volumetric capacity ofthe grinding 'cham- 1 bers, as by forming the mill withV chambers Y Y v Vcreases as the mass of` the grinding body 1ntrarlly fixing the partltlon Withln the mill Y of material -being ground. Any increase be? a mill had been thus constructed, each cham- Y yond this 'willcause the efiiciency of grind ber was filled substantially to the centerline ing to again fall olf. l l

For these reasons it has heretofore been- Size or welght, and a test run of the mill with ,grinding bodies properly graded in'l Y. customary/in installations having a comwas made. lIf the arbitrarily predetermined y vnary coarse grinding, delivering to a fine- -Ygrinding tube mill. 50V

paratively extended range 'of reduction, to size of the first'chamber was'tool largeA in utilizefseveral millsY in Series, as, for inrelationrto the'size of the second, this fact stance, a ball mill for efectingjthe prelimi` would be indicated by the fact that the the second, is finer than necessary for the It has also bcenproposed to utilize the sosecond chamber, the result being that the called. combination mill,in"which a single first chamber? would operate ineficiently.

partitions, in the one chamber of which mill l decreasing the charge of bodies in material passing from the rst chamber to 'rotary drum is dividedfintoA two or more Thisl defect could only be lessened, there grinding chambers sepa-rated by one or more belng no means for further correction, by-A orf `ber were too small in relation to the second,`

the first chamber substantially below the centerline decreasing the power somewhat, but thereby violating the law of centerline loading for maximum efficiency, the result..

being that the mill would still run at less` than maximum efficiency. If the' first chamthis condition would be indicated, first, in the case Where fine screens prevent too coarse a product from leaving the first chamber, b the fact that the finished product wouldy e finer than the required standard, and by the further fact that the first chamber fills up. with insufficiently ground material on attempting to increase the rate of feed to such an amount'as to make a coarser finished product; and second, in the case where material from the first chamber has free access to the second chamber regardless of whether it has been properlyground inthe first chamber or not, by the act that the secondI .chamber will 'either' become filled with particles too coarse to be ground by its grinding bodies, or, these particles, of slze largert shortly pass out with the finished product. vThe product leaving the mill may therefore power somewhat and decreasing the ca.

temporaril be of the standard degree of fineness. his defect can only be lessened by decreasingthe amount of grinding bodies in the'second chamber substantially below the centerline, thereby decreasing thel horse pacity of the second chamber to that of the firstA when the first chamber is delivering material pf roper size, therefore a ain violating the aw of centerline loa 'ng' for maximumieficiency as stated above., Fur- -.thermo re, in addition to. the loss in ef1i ciency, tlrtotal capacit of agiven size of null in either. 'case .is ecreased below the maximum capacity attainable when the two chambersl are properly pro ortioned.

The. present inventlon e ects efficient. op-

@ration of combination mills by apportionfing lthe work done in the chambers thereof,

the chargel of grinding bodies being maintained at the most efficient centerline point' as heretofore explained whereby 1 s1elfecte a maximum rate 'of grinding materia'l''to a predetermined degree of fineness 4a inmimum,e$xpenditure of energy'. -clear conceptlon of. the vvarious steps "ofthepresent process .and of one form of apparatus vfnor carrying on4 the same maybe f lfiad fro'mthe drawing accompanying and a part of this specification'in which like 1"e' eren'ce characters designate 'the same or simllar 4parts in the various views.

Figure l1 is-a diagrammatic centralverembodying a Aform o an the standard, willv tical section throu h a combinationv mi1l the invention in which a partition is `adjustable to vary the volu-` metric capacities of .the several chambers.

' Fig. 2 1s. an enlarged .fragmentary central` vertical section through a combination mill having an adjustable partitlon. Fig. 3 is an enlarged fragmentary transverse vertical section through the mill, the

section being'taken along the line III-III of Figs. 2, 5 and 6 looking in the direction' of the. arrows.

Fig. 4 is an enlarged fragmentarytransl verse vertical section through the mill, the

Fig. 6 .is an 'enlarged'fragment of a de# velopment of a section through the mill, the section being taken along 1the lines VI-VI of Figs. 2 and 3, looking in the direction of the arrows.

The combination mill illustrated as one form embody-ing this'invention,comprises a 'rotary `shell 1 having feed and discharge end heads 2, 3,'respectively, and provided with an adjustable partition 4 dividing the shell 1 into chambers 5, 6. The mill is ro-l tatably mounted in bearings 7,. 8, and is adapted to be rotated by power applied to the driving gear 9.

The coarse grinding chamber 5 is filledA substantially to the centerline of the shell 1 vwith relatively large comminuting balls 10, while the fine grinding or finishing chamber 6 is likewise half-filled with relatively small comminuting bodies or balls 11V. The bodiesorballs 10, 11,'.are preferably formed of,'iron or other material having high.' specific weight. The coarse grinding chamber 5 receives its supply of relatively `coarse material through the feed trunnion` 70 and delivers the material in partially refduced conditiomthrough the partition 4 tono the finishing chamber 6 from which the finished product is delivered through the of elevating plates 12'.

The adjustable partition@ comprises a !holdback .screen 13, and a centrally perforated end 'wall 15, these elements being 'dischar'ge'trunnion 80 by meansy of ase'ries' 4spaced apart to formja chamber v16. The

.portion of'thexshell 1 within the limits of adjustment ofthe partitionfl is provided.

w ith af circumferential series of elongated opemngs 18' which communicate-with an 'annular chamber divided by means of the circular screen 19 intoV two annular chambers` 20, 21. The portions of the openings- 18 which arebeyond the llimits ofthe. partition 4 are normally covered by liners' 22,' 23, of disarm widths measured. iongii tudinally Vof .the mill. The .liners v22 .in the chamber 5 may of thesame thickness as the liners. 23 in the chamber 6, or they may be of different thicknesses as disclosed,

lthe liners 22, 23 as well as the balls 10, 11

being insertible and removable through manholes in the shell 1, such holes having beenomitted from the drawing on account of the customary provision thereof in mills of this type. n The chamber 16 adjacent the holdback screen 13 communicates directly `with the annular chamber through the openings l18 so that material delivered through the screen 13 passes directly through the openings 18 to.the interior of the circular sizing screen 19. Reject collecting plates 24 located withinthe chamber 20 are 'adapted to lcollect material which cannot pass through the sizing screen 19 and to deliver this oversize into return conduits leading from the chamber 20 into the coarse grinding chamberv 5 ofthe mill. The chamber/21 loca-ted exteriorly of the sizing screen 19g/,is provided with collecting plates 26 which collect the fines passing through the sizing screen 19 anddeliver these fines into the conduits 27 leading from the chamber 2 into the fine grinding chamber 6 of the mill. The conduits 25, 27, are located with- -in the chamber 16 adjacent the wall 15, and

do not interfere with the passa-ge of mater rial through the holdback screen 13. The material passing through the conduit-s 27 is fed to the chamber 6 through the opening 30 in the wall'15 and the finished product delivered from this chamber 6 is delivered to the elevating plates 12 through the rdischarge screen 29.

In carrying out the process of this invention, the partition 4 vis first located somewhere within the limits of the openings 18 and the chambers 5, 6, are filled substantially up to the mill axis with 'comminuting balls 10, 11. The mill is then rotated and the feed of material through the trunnion 70 is gradually increased until the requisite lfineness offdischarge product does not ex-4 -and the partition end of the mill',`-\the level of the balls10 1 'being-maintained shifting ofthe partition 4'toward the feed 'ceed that necessary for standard cement.

The next step is to balance the mill, that is, place the -several chambers in condition to g'iind the material passin therethrough wit maximum efficiency. n the present invention this is 'done by adjusting the.

partition 4, without any sacrifice vfromthe condition of maximum capacity.

The condition of theA material atthe end of the coarse grinding chamber is then dere'moving a sample through a from a lchamber 20,21 and'by 1f the material termined by manhole o r subsequent screen analysis.

here isy found from prior practiceto-be too.'y

fine-for maximum'efliciency of this chamber, the quantity oflarge'balls 10 is reduced 4 moved toward the feed constant.' Due to. this end ofthe mill, the quantity off sm all balls ber 6 will be only enough coarser so as to be of the required ineness. TheV condition of the material at the' discharge end of the coarse rinding chamber 5 is then again noted. f it is then found from prior practice to be too coarse for` maximum efficiency of this chamber, the chamber is lengthened by moving the partition 4 tof.

wardthe discharge 'end ofthe mill and corJ- 0 respondingly increaslng the quantity large balls 10. The resulting increase 1n large grinding bodies will now deliver the materiaLto the finishing chamber liner than before so that the final product will be too fine and the feed may be increased. Ad-. justment of the partition 4 is continued until a point is reached where a maximum disof material atthe proper neness re- It will be noted that during these adjustments, the charge of grinding balls is maintained substantially at the centerline of the mill/'byv insertion or removal of balls l0, 11 through the manholes', and the power required to operate the mill stantially constant. maximum capacity, the horse power -hours per barrel, which is the accepted standard of determining the efliciency of a mill, will be the lowest, that is,

charge llVhilethe drawings disclose the. use of a partition 4 of special construction, it will be noted that such special construction is not necessary in carrying out the present inven-v tion, andl that an ordinary partition consisting offa perforated diaphragm. maybe em ployed. v

lThe. adjustment of the partition 4 in the vj aresent case'is accomplished-by interchanging some of the liners 22, 23, access to the interior of the lmill for the purpose of interchanging these liners being had through the manholes. The plates 24, 26, must also be changed in order to maintain proper alineare within 'the chambers 20,

4. For instance, 1f it is' desired to adjust, the partition- 4 toward the feed `end ofth mill a slight amount only, it is necessary only to interchange the liners directly'adj athe maximum efliciency will have been'attained.

will be sub- Upon reaching the ment betvveenvthel portions of the conduits 25 -.27, which 21, and those portions within the partition centthe'partition. If a greater adjustment is" desired, the necessary adjustmentcf' liners to produce the ment of the partiti Ordinarily, the li nient of the parti yond the limits closed, but it W openings may b in the limits of th commodate th ment.

In the structure di delivered from the coa 5 passes through the h is precipitated upon screen 19. -As the mill tion indicated by the arr the material rolls alon being' eventually pre turn -plates 24 and ding compartme 25. The fines W J` screen 19 are eventua the plates 26 and are en d of the finishing o n his grin duits of the material by the c It should be underst `sired to'limit `the pre s of the pr details of co hown and d ons lwill occ in the art.

It,is claim'e ters P t 1. rlhe method of' exact step the exact para'tus s lmodificati contin consists inb primary cha chamber at anormal .the material ground -in the efficiency of operation' ing the relativevolumet elivered int chamber 6 th ings 30 by mea construction of the efficient removal of the 30 nstruction of t escribed, for o mill provided -ondary grinding ch consists in l. primary chambe -ary chamber at a normal changing the lrelative vol of said chambers and-'ma' dinghlevelrtherein, and su uin t e. rindlng' chambersgas chaigi d.

3 2. The met tube Vmill ding the m rV and then liod Qf provided vwith Io'ndary grinding chaibe gnding 'tb mber and th ambers in order -t'o'gi of operation as determi maintaining thev 'normal said chambeis, and subseq desired degree of adjustthe grinding operation in said chambers as on may readily be made. changed.

mits of necessary adjust-4 3. Ihe process of apportioning the Work tion 4 will not extend bedonein th'e several chambers of-a combinaof the openings 18 as distion comminuting mill to produce maximum 70 111 be apparent that these grinding capacity and eiiiciency, Which comany length With-- prises producing chambers of arbitrary volu e shell 1, suliicientto ac metric grinding capacities, loading one of e desired degree ef adjustsaid chambers lto the 'center line ofthe mill with coarse grinding bodies, loading another sclose'd, the I naterial4 0f said chambers to the center line of the rse grinding chamber mill vvith fine grinding bodies, admitting oldbaek Screen 13 and material to the mill and operating the mill the circular sizing to comminu te the admitted material, ascerrotates in the dreetaining the condition of the material in the ows in Figs. 3 and 4, mill, and relatively varying the volumetric g the surface 0f the grinding capacities of said chanrbers Withpassing through this out altering the level of the charges of grinder 21` and the oversize ing bodies and .continuing the. grinding of cipitated upon the rethe partially ground material in the changed returned to the coarse chamber until the required iineness for the t 5 through the condischarged material is obtained.' hich-pass through the '4. -In a comminuting mill, a rotary shell,

y precipitated upon means forming achamber surrounding and o the feed extending 'longitudinally of saidshell, said 90 rou h theA shell being perforated vadjacent'said chamf the conduits 27. ber and said perforations extending along partition permits the` entire length of said chamber measured sufficiently reduced longitudinally ofy the mill, a -partition adgrinding chamber-5, justable axially of said shell at said perfoessary line grinding rations,said partition being of less Width oarse grinders. ood that it is not de-v perforated portions of said shell are located sent inventionl to the beyond said'partition, and means for closing cess described or to thre perfrations located beyond said parti-4 100 he aption.

than the length of ,said chamber whereby bvious 5. In a' comininutingimill, a rotary shell, ur to a person Vskilled means forming a chamber surrounding' said' shell, a 'screen within said chamber, said d and desired to secureby Letshell having a plurality of openings extending longitudinally of said s lioell and located grinding material in a adjacent said chamber, a partition adjustwith' primary -and `secable axially of said shell at said openings,` which method saidl partition being of less width than the aterial in said length'of saidl openings, means for closing l10- i`n said second- 'the portions of s aid, openings projecting begrind'mg level, yond said partition, means within said parumetric ca vacitiel tition'v for returning rejects from said screen t e ndrto one of said chambers, and means within uently fsaid vpartition for delivering material mss# operation; in "said ing said screen to another of said chambers'.

' 6. In a comminuting mill, la shell, a

ding material in ascreening partition adjustable longitudinally primary and sec-A of said' shell, and.' means lfor effecting access rs, which vmethod to said partition through said shellat the 120 e material in' said peripheryof said partition. en in said secondary nl a comininutin -m1l, va shell, a

ng level, testing screening partition er to determine nally of said shell, means 'formin `al chamof the mill, c'hang---- ber surrounding-an .extending I ric capacities of said Vnally of'said shell a jacent to the eriphery prove the eiiciency of'said partition, and means fore ecting acd b'y said test 'and 'cessio said partition through said' chamber. grinding level in 8. The-method of rindin in a tube mill uentlycontinuing having primaryan secon ry chambers,

Justable longitudifv.

which method consists. in a preliminary grinding until the fineness of the dischargedv material does' not exceed that required, changing the relative volumetric capacities of the chambers While maintaining the congrinding in said changed chambers and increasing the feed untilthe required ineness of ground material is obtained.

In testimony whereof, the signature of the inventor is aixed hereto.

PAUL C. VAN ZANDT. 

